Semiconductor device and electronic apparatus using the same

Abstract

The transistor suffers the variation caused in threshold voltage or mobility due to gathering of the factors of the variation in gate insulator film resulting from a difference in manufacture process or substrate used and of the variation in channel-region crystal state. The present invention provides an electric circuit having an arrangement such that both electrodes of a capacitance element can hold a gate-to-source voltage of a particular transistor. The invention provides an electric circuit having a function capable of setting a potential difference at between the both electrodes of the capacitance element by the use of a constant-current source.

What is claimed is: 
     
       1. A semiconductor device comprising:
 a first transistor; 
 a second transistor; 
 a first capacitor; 
 a second capacitor; 
 a third capacitor; 
 a first switch; 
 a second switch; 
 a third switch; 
 a fourth switch; 
 a fifth switch; 
 a sixth switch; 
 a seventh switch; 
 an eighth switch; and 
 a ninth switch, 
 wherein the first transistor and the second transistor have the same polarity, 
 wherein a gate of the first transistor is electrically connected to one terminal of the first capacitor and one terminal of the sixth switch, 
 wherein the other terminal of the first capacitor is electrically connected to one terminal of the first switch and one terminal of the second switch, 
 wherein the other terminal of the second switch is electrically connected to one of a source and a drain of the first transistor, one of a source and a drain of the second transistor, one terminal of the fourth switch, and one terminal of the eighth switch, 
 wherein the other terminal of the eighth switch is electrically connected to one terminal of the third capacitor and one terminal of the ninth switch, 
 wherein the other of the source and the drain of the first transistor is electrically connected to one terminal of the fifth switch, 
 wherein the other terminal of the fourth switch is electrically connected to a gate of the second transistor and one terminal of the second capacitor, 
 wherein the other terminal of the second capacitor is electrically connected to the other of the source and the drain of the second transistor, 
 wherein the other of the source and the drain of the second transistor is electrically connected to a first power supply line, 
 wherein one terminal of the third switch is electrically connected to one terminal of the seventh switch, 
 wherein the other terminal of the first switch is electrically connected to an input terminal, and 
 wherein the other terminal of the third switch is electrically connected to an output terminal. 
 
     
     
       2. The semiconductor device according to  claim 1 ,
 wherein the other terminal of the sixth switch is electrically connected to the other of the source and the drain of the first transistor. 
 
     
     
       3. The semiconductor device according to  claim 1 , further comprising a tenth switch,
 wherein one terminal of the tenth switch is electrically connected to the other of the source and the drain of the first transistor. 
 
     
     
       4. The semiconductor device according to  claim 1 , further comprising a third power supply line electrically connected to the other of the source and the drain of the first transistor. 
     
     
       5. The semiconductor device according to  claim 1 , further comprising a current source electrically connected to the other of the source and the drain of the first transistor. 
     
     
       6. The semiconductor device according to  claim 1 , further comprising:
 a tenth switch; and 
 a third power supply line, 
 wherein one terminal of the tenth switch is electrically connected to the other of the source and the drain of the first transistor, and 
 wherein the other terminal of the tenth switch is electrically connected to the third power supply line. 
 
     
     
       7. The semiconductor device according to  claim 1 , further comprising:
 a tenth switch; and 
 a current source, 
 wherein one terminal of the tenth switch is electrically connected to the other of the source and the drain of the first transistor, and 
 wherein the other terminal of the tenth switch is electrically connected to the current source. 
 
     
     
       8. The semiconductor device according to  claim 1 , further comprising:
 a current source; and 
 a third power supply line, 
 wherein one terminal of the current source is electrically connected to the other of the source and the drain of the first transistor, and 
 wherein the other terminal of the current source is electrically connected to the third power supply line. 
 
     
     
       9. The semiconductor device according to  claim 1 , further comprising:
 a tenth switch; 
 a current source; and 
 a third power supply line, 
 wherein one terminal of the tenth switch is electrically connected to the other of the source and the drain of the first transistor, 
 wherein the other terminal of the tenth switch is electrically connected to one terminal of the current source, and 
 wherein the other terminal of the current source is electrically connected to the third power supply line. 
 
     
     
       10. The semiconductor device according to  claim 2 ,
 wherein the other terminal of the fifth switch is electrically connected to a second power supply line. 
 
     
     
       11. The semiconductor device according to  claim 2 ,
 wherein the other terminal of the seventh switch is electrically connected to a second power supply line. 
 
     
     
       12. The semiconductor device according to  claim 1 , further comprising a fourth transistor,
 wherein one of a source and a drain of the fourth transistor is electrically connected to a second power supply line, and 
 wherein the other of the source and the drain of the fourth transistor is electrically connected to the other terminal of the fifth switch. 
 
     
     
       13. The semiconductor device according to  claim 1 , further comprising a fifth transistor,
 wherein one of a source and a drain of the fifth transistor is electrically connected to a second power supply line, and 
 wherein the other of the source and the drain of the fifth transistor is electrically connected to the other terminal of the seventh switch. 
 
     
     
       14. The semiconductor device according to  claim 1 , further comprising a sixth transistor,
 wherein one of a source and a drain of the sixth transistor is electrically connected to the one terminal of the seventh switch, 
 wherein the other of the source and the drain of the sixth transistor is electrically connected to the other terminal of the second switch and the one terminal of the eighth switch, and 
 wherein a gate of the sixth transistor is electrically connected to the other terminal of the third capacitor. 
 
     
     
       15. The semiconductor device according to  claim 1 , wherein the other terminal of the ninth switch is electrically connected to a second input terminal. 
     
     
       16. The semiconductor device according to  claim 1 , wherein the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, the eighth switch and the ninth switch are each a transistor. 
     
     
       17. An electronic apparatus comprising the semiconductor device according to  claim 1 . 
     
     
       18. A display device comprising:
 a pixel portion over a substrate; and 
 a source follower circuit over the substrate, the source follower circuit comprising:
 a first transistor; 
 a second transistor; 
 a first capacitor; 
 a second capacitor; 
 a third capacitor; 
 a first switch; 
 a second switch; 
 a third switch; 
 a fourth switch; 
 a fifth switch; 
 a sixth switch; 
 a seventh switch; 
 an eighth switch; and 
 a ninth switch, 
 
 wherein the first transistor and the second transistor have the same polarity, 
 wherein a gate of the first transistor is electrically connected to one terminal of the first capacitor and one terminal of the sixth switch, 
 wherein the other terminal of the first capacitor is electrically connected to one terminal of the first switch and one terminal of the second switch, 
 wherein the other terminal of the second switch is electrically connected to one of a source and a drain of the first transistor, one of a source and a drain of the second transistor, one terminal of the fourth switch, and one terminal of the eighth switch, 
 wherein the other terminal of the eighth switch is electrically connected to one terminal of the third capacitor and one terminal of the ninth switch, 
 wherein the other of the source and the drain of the first transistor is electrically connected to one terminal of the fifth switch, 
 wherein the other terminal of the fourth switch is electrically connected to a gate of the second transistor and one terminal of the second capacitor, 
 wherein the other terminal of the second capacitor is electrically connected to the other of the source and the drain of the second transistor, 
 wherein the other of the source and the drain of the second transistor is electrically connected to a first power supply line, 
 wherein one terminal of the third switch is electrically connected to one terminal of the seventh switch, 
 wherein the other terminal of the first switch is electrically connected to an input terminal, 
 wherein the other terminal of the third switch is electrically connected to an output terminal, 
 wherein the pixel portion comprises a third transistor and a display element, 
 wherein the third transistor is electrically connected to the display element, and 
 wherein the source follower circuit is operationally connected to the pixel portion. 
 
     
     
       19. The display device according to  claim 18 ,
 wherein the other terminal of the sixth switch is electrically connected to the other of the source and the drain of the first transistor. 
 
     
     
       20. The display device according to  claim 18 , further comprising a tenth switch,
 wherein one terminal of the tenth switch is electrically connected to the other of the source and the drain of the first transistor. 
 
     
     
       21. The display device according to  claim 18 , further comprising a third power supply line electrically connected to the other of the source and the drain of the first transistor. 
     
     
       22. The display device according to  claim 18 , further comprising a current source electrically connected to the other of the source and the drain of the first transistor. 
     
     
       23. The display device according to  claim 18 , further comprising:
 a tenth switch; and 
 a third power supply line, 
 wherein one terminal of the tenth switch is electrically connected to the other of the source and the drain of the first transistor, and 
 wherein the other terminal of the tenth switch is electrically connected to the third power supply line. 
 
     
     
       24. The display device according to  claim 18 , further comprising:
 a tenth switch; and 
 a current source, 
 wherein one terminal of the tenth switch is electrically connected to the other of the source and the drain of the first transistor, and 
 wherein the other terminal of the tenth switch is electrically connected to the current source. 
 
     
     
       25. The display device according to  claim 18 , further comprising:
 a current source; and 
 a third power supply line, 
 wherein one terminal of the current source is electrically connected to the other of the source and the drain of the first transistor, and 
 wherein the other terminal of the current source is electrically connected to the third power supply line. 
 
     
     
       26. The display device according to  claim 18 , further comprising:
 a tenth switch; 
 a current source; and 
 a third power supply line, 
 wherein one terminal of the tenth switch is electrically connected to the other of the source and the drain of the first transistor, 
 wherein the other terminal of the tenth switch is electrically connected to one terminal of the current source, and 
 wherein the other terminal of the current source is electrically connected to the third power supply line. 
 
     
     
       27. The display device according to  claim 18 ,
 wherein the other terminal of the fifth switch is electrically connected to a second power supply line. 
 
     
     
       28. The display device according to  claim 18 ,
 wherein the other terminal of the seventh switch is electrically connected to a second power supply line. 
 
     
     
       29. The display device according to  claim 18 , further comprising a fourth transistor,
 wherein one of a source and a drain of the fourth transistor is electrically connected to a second power supply line, and 
 wherein the other of the source and the drain of the fourth transistor is electrically connected to the other terminal of the fifth switch. 
 
     
     
       30. The display device according to  claim 18 , further comprising a fifth transistor,
 wherein one of a source and a drain of the fifth transistor is electrically connected to a second power supply line, and 
 wherein the other of the source and the drain of the fifth transistor is electrically connected to the other terminal of the seventh switch. 
 
     
     
       31. The display device according to  claim 18 , further comprising a sixth transistor,
 wherein one of a source and a drain of the sixth transistor is electrically connected to the one terminal of the seventh switch, 
 wherein the other of the source and the drain of the sixth transistor is electrically connected to the other terminal of the second switch and the one terminal of the eighth switch, and 
 wherein a gate of the sixth transistor is electrically connected to the other terminal of the third capacitor. 
 
     
     
       32. The display device according to  claim 18 , wherein the other terminal of the ninth switch is electrically connected to a second input terminal. 
     
     
       33. The display device according to  claim 18 , wherein the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, the eighth switch and the ninth switch are each a transistor. 
     
     
       34. A display module comprising:
 a FPC; and 
 the display device according to  claim 18 . 
 
     
     
       35. An electronic apparatus comprising:
 the display module according to  claim 34 ; and 
 at least one of a speaker, an image receiving part, an external connection port, a battery, a sound input part, and a second capacitor antenna.